Adhesive, brittle resin processes

The achievement of enhanced toughness in a brittle polymer such as an epoxy resin is vital in applications such as adhesives, for which peel strength and resistance to interfacial debonding through crack propagation are important criteria for performance. This may be achieved by incorporation of elastomeric or other phase-separated particles into the network. These may be present before reaction or they may form during the process of... 

It was noted in the previous section that the carboxyl end groups on the CTBN elastomer affected the final performance of the material as a toughener since these groups would co-react with the epoxy resin and facilitate stress transfer from the brittle matrix to the phase-separated elastomer. Without this adhesion the particles could debond prematurely, which would lead to poor dissipation of the energy of the growing crack. It has also been noted that excessive adhesion between an epoxy resin and a thermoplastic could be deleterious to the performance (Williams et al, 1997). The process of toughening of a thermoset... 

Non-woven fabrics are formed directly from short fibers that are assembled in sheets. The fibers are connected together to enhance the handlability of such sheet of otherwise loose fibers. Rows of needles are sometimes used to punch through the sheet of fibers and reorient some of the fibers to achieve mechanical adhesion between the fibers (needle punched fabrics). This process, although very successful with polymer fibers such as para-aramids, has less success with brittle ceramic fibers such as glass and carbon because fibers can easily break. Another method used to connect the short fibers is by using an adhesive to glue the short fibers to one another. In the case of short fiber composites, this glue will typically have a chemical affinity to the resins. 

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